For many years our laboratory has investigated the chemistry of certain natural products from plants and microorganisms. The rationale for these investigations is that the natural products possess unique biological properties. We will continue our investigations of steroidal plant-growth hormones (brassinosteroids). Several of these steroids have been synthesized in our laboratory. We hope to synthesize tritiated brassinolide and to use this compound to search for the receptor of the hormone in plant cells. Investigation of new anticancer agents derived from the fungal sesquiterpene illudin S will continue. We have identified two derivatives which show great promise in treatment of solid tumors. We plan to prepare more derivatives and to study the mechanism of their anticancer action.